Electrochemical batteries are widely used and are important particularly with rechargeable type batteries for use in a wide variety of apparatus ranging from laptop computers to automotive vehicles particularly with hybrid and all electric vehicles.
It is known that batteries degrade overtime. A rechargeable battery loses its capacity i.e. the total amount of energy available lessens over time regardless of its state of charge. Is it thus desirable to know not only the state of charge of a battery i.e. its level of stored energy which consolidates to the open circuit voltage (OCV) but also the capacity for storing energy. Often the capacity of the battery compared to its rated capacity when new is referred to as its state of health. When the capacity becomes too small it may not support auxiliary loads and possibly cranking events for automotive applications and the battery is said to have reached the end of its useful life.
A method for determining battery capacity is known where the current is a ramped until the voltage is observed to rise rapidly. The peak in voltage relates to the present state of charge or available energy of the battery. The ramping of current requires control of the charging current which is usually lacking in conventional automotive vehicles.
Another known method for determining battery capacity requires the battery to discharge to a low state of charge. A time amp hour integration is used to track the energy input during a charging cycle. However deep discharge cycling is not practiced in most hybrid or conventional vehicles due to battery damage at low states of charge and loss of battery related functions.
What is needed is a method that provides a determination of battery capacity without the need for controlled current or deep discharge of batteries.